This invention relates to an age old problem that goes back to when oil was first stored in tanks or vessels. The term "crude oil" refers to oil recovered from below the earth's surface which remains "untreated" or unrefined. The problem begins when contaminants settle out in the bottom of oil storage tanks. Contaminants come from various sources and some of the contaminants are indigenous to the crude oil itself. Sludge forms when naturally occurring solids (formation sands) as well as rust and scale from piping and tank walls, and higher molecular weight hydrocarbons separate from lighter hydrocarbons and sink to storage tank bottoms. Over time, this matter referred to as sludge, sludge oil or tank bottoms forms on the bottom of the tank or storage vessel. Operators (personnel involved with oil facilities) must deal with this sludge problem, as it hampers normal procedures and increases oil handling and treatment costs. Tanks are also required to be routinely inspected for structural integrity, involving such concerns as possible leaks, damage and corrosion.
Past methods for cleaning contaminants involved mechanical removal of the contaminants by vacuum trucks and hydroblasting equipment, e.g. bob cat, dragline and robotics to name a few. These methods require entry into the tank by authorized personnel. Little was done to reduce the volume of the contaminants prior to removal.
Then came the use of chemical methods, using hot water and diluent. A Nalco Chemical process (See U.S. Pat. No. 5,085,710 Date Feb. 2, 1992), relies on chemicals to reduce the oil mass in sludge oil bottoms. These chemicals are not environmentally engineered, and are considered harmful to living organisms.